A DC-to-DC power converter typically steps down voltage while stepping up current, from its input supply to its output load. It is a class of switched-mode power supply (SMPS) typically containing at least two semiconductors (a diode and a transistor, although modern buck converters frequently replace the diode with a second transistor used for synchronous rectification) and at least one energy storage element, a capacitor, inductor, or the two in combination. To reduce voltage ripple, filters made of capacitors (sometimes in combination with inductors) are normally added to such a converter's output and input. Switching converters provide much greater power efficiency as DC-to-DC converters than linear regulators, which are simpler circuits that lower voltages by dissipating power as heat, but do not step up output current.
There are several topologies in a power supply application. A well-known topology is the buck converter. Other topologies such as resonant, flyback or forward converter are also used. Some topologies use a low side as well as a high side switch. The disadvantage of a high side switch is that it requires a dedicated supply. For the dedicated supply, a booststrap supply circuitry, consisting of a diode and a capacitor, may be used. This circuitry needs to be supplied from a supply which output voltage is sufficient to drive the external MOSFET (typical minimum voltage 8V), but must always remain below the maximum drive voltage of the external MOSFET (typically 20V). As this voltage is not always available in a typical power supply, it needs to be either provided by the control IC or derived from a dedicated circuitry.
The disadvantage of a dedicated circuitry is the additional components, which goes at the cost of area (form factor) and costs. For this reason, several control integrated circuits (IC's) provide a dedicated supply via a dedicated pin. However, the form factor of a power supply must be minimized to such that even the pin count of a control IC must be minimized. Which then also reduces the cost even further.